In the process of producing a semiconductor device such as IC and LSI, microfabrication by lithography using a photoresist composition has been conventionally performed. Recently, with the increase in integration degree of an integrated circuit, formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using electron beam, X-ray or EUV light is also proceeding.
The lithography using electron beam, X-ray or EUV light is positioned as a next-generation or next-next-generation pattern formation technology and a high-sensitivity and high-resolution resist composition is being demanded.
Particularly, in order to shorten the wafer processing time, elevation of sensitivity is very important, but when higher sensitivity is secured, the pattern profile or the resolution indicated by the limiting resolution line width is deteriorated, and development of a resist composition satisfying all of these properties at the same time is strongly demanded.
High sensitivity is in a trade-off relationship with high resolution and good pattern profile, and it is very important how to satisfy all of these properties at the same time.
In order to solve such a problem, for example, in JP-A-2008-33287 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JPA-2008-31160, JP-A-2000-29215 and JP-A-2004-45448, a positive resist composition using a resin having an acetal-type protective group is disclosed, and it is demonstrated that according to this composition, resolution, sensitivity and the like are improved.
In recent years, a pattern forming method using an organic solvent-containing developer (organic developer) is being also developed, and it is indicated that according to this method, a high-definition fine pattern can be stably formed.
Furthermore, needs for formation of a fine isolated pattern are abruptly increasing in recent years, and to meet the needs, in forming a fine isolated pattern with a narrow line width, more improvements are required on the sensitivity, resolution, PEB (post-exposure baking) temperature dependency, pattern profile and etching resistance.